A Z0-match is defined in my ARRL Antenna Book.

Sorry, I have that book, but I do not remember where it is.

Here is an example of a Z0-match to 50 ohms at point '+':

XMTR--50 ohm coax---+---1/2 WL 300 ohm feedline---50 ohm load


OK, understood.

The SWR on the 300 ohm feedline is 6:1. The SWR on the 50
ohm coax is 1:1. What happens to the energy and momentum
of the reflected waves on the 300 ohm feedline? Seems
obvious that there is destructive interference toward
the XMTR and constructive interference toward the load.

I am not sure on whether I am able to correctly interpret your statement. My
understanding is:

- reflected power does not reach the transmitter, as it is fully reflected back
toward the load
- such re-reflected power reaches the load, where it is partially absorbed (thus
contributing to the total power delivered to the load) and partially reflected
back once more

Probably this is what you call destructive interference at the trasmitter and
constructive interference at the load.

The fact that reflected power is fully re-reflected to the load does not seem to
be appreciated by everyone. Many people still attribute their transmitter power
transistors failure to reflected power burning them. The failure is instead
clearly due to malfunctioning or poor design of the SWR protection circuit that:
- does not keep the collector voltage within its maximum allowable value when
load impedance is too high
- does not keep the collector current and the junction temperature within their
maximum allowable values when load impedance is too low

73

Tony I0JX